Izvestiya, Physics of the Solid Earth最新文献

A description of the evolution of a spherical block model of the dynamics and seismicity of the lithosphere is given. The main focus is on the current version and the introduction of a constructive automatic calibration (parameter selection) procedure to obtain the best approximation of key properties of regional and/or global seismicity. The paper presents some results of computational experiments.

The article presents the general results of medium- and long-term earthquake forecasting with K ≥ 13 (M ≥ 5.0) in the Baikal rift zone. They were obtained in recent years through the joint use of the Prediction geoinformation system and the developed two-stage phenomenological model for the periods of preshock preparation of earthquakes. This model was created based on the analysis of seismological data on the preparation of the most dangerous local earthquakes that occurred in the Baikal rift zone. It is consistent with results obtained in the study of seismic regimes of ice shock preparation on the ice cover of Lake Baikal and in conducting field experiments on fault sections with the aim of clarifying the physical and mechanical conditions for the emergence of sources of seismic-range wave-oscillation generation. The paper provides an example of practical use of the obtained results of earthquake forecasting, as well as methods of clarifying seismic-hazard assessments in relation to infrastructure in the city of Angarsk, located 100 km from the seismically dangerous Main Sayan Fault (MSF), in the zone of which, during the analysis of the seismic regime, a “locked” segment with a seismic gap was identified. In accordance with its linear dimensions with a length of 60 km, according to two assumed equations of relationships L/M, estimates of energy potential were calculated, the maximum values of which correspond to the values M_max = 7.1 and 7.8. It is shown that the use of the obtained earthquake-forecast results helps to clarify the level of seismic hazard for the nearest time intervals of expectation of earthquakes with different values M_max. An example of assessing the current seismic hazard using a medium-term forecast for the infrastructure of the city of Angarsk is considered for possible seismic tremors from the south-eastern section of the MSF zone for the next 10 and 50 years. When compared with the OSR-16 map, it is shown that the calculations carried out indicate a relatively lower level of seismic hazard for the city of Angarsk, with waiting times of 10 and 50 years.

The issue of the occurrence of seismicity induced by injection of fluid into the subsurface is considered. A model of nested fractures is presented, which allows simulating the process of fluid filtration in a rock containing fractures or faults, taking into account the change in the filtration properties of the latter during the change in pore pressure. The process of fault deformation is described using the displacement discontinuity method. The model is used to analyze the effect of fluid injection in the immediate vicinity of a fault on its subsequent deformation. The transition of fault slip from aseismic to seismic is investigated when the parameters of the friction law or fluid injection parameters change. Conditions have been found under which seismic slip may occur within the framework of the proposed model.

Abstract—The spatial clustering of epicenters of seismic events in the Northwest Pacific Ocean is analyzed using the Discrete Perfect Sets (DPS) topological filtering algorithm. The results of the analysis are presented in this paper. Based on the data shallow earthquakes recorded from 1963 to 2022 by the seismic network of the Kamchatka Branch of the Geophysical Survey of the Russian Academy of Sciences, stable areas of epicenter clustering are identified. These areas are associated with the Northern and Southern segments of the Kuril-Kamchatka seismofocal zone and do not depend on the time of recording of the earthquakes. The characteristic clustering radius for the Kuril-Kamchatka seismofocal zone is determined and is found to be 42–44 km. The analysis has confirmed the unique pattern of seismicity in the territory of the Commander segment of the Aleutian arc, which differs from that observed in the Northern and Southern segments.

In this paper, we present a description of a database of earthquake focal mechanisms, which is compiled from the data of international seismological agencies and literature sources for the East Arctic region. It consists of 595 focal mechanism solutions for 273 seismic events with M = 2.1–7.6, which occurred in 1927–2022. Information about the source depth, the scalar seismic moment, and the moment magnitude are also presented there for many events. In addition to the focal parameters, their quality assessments are available, which facilitates a comparison of different solutions in many cases. For user convenience, the database has a graphical interface that permits searching by various attributes (coordinates, time, magnitude, and depth). In terms of volume of the collected information, our database significantly exceeds all the analogues available at the present time. It can be used to perform a seismotectonic analysis, to estimate the stress–strain state of the lithosphere, and to assess seismic hazard for the entire East Arctic region or its separate areas. Implementation of the compiled database for comparison of different solutions of earthquake focal mechanisms and their seismotectonic analysis is illustrated in the paper on the example of seismic events occurred in the Olenek Bay of the Laptev Sea and adjacent territories. We suggest adding new information to the database every five years in future.

Abstract—The Gutenberg–Richter law establishes a log-linear relationship between the number of earthquakes that have occurred within some spatiotemporal volume and their magnitude. This similarity property presumably reflects fractal structure of the fault system in which earthquake sources are formed. The Gutenberg–Richter law plays a key role in the problems of seismic hazard and risk assessment. Using the Gutenberg–Richter relationship, we can estimate the average recurrence period of strong earthquakes from the recurrence rate of weaker earthquakes. Since the strongest earthquakes occur infrequently, with intervals of a few hundred years or more, it is not possible to directly assess their recurrence. From indirect geologic and paleoseismic estimates it often seems that strong earthquakes on individual faults occur more frequently than expected in accordance with the Gutenberg–Richter law. Such estimates underlie the hypothesis of the so-called characteristic earthquakes. This hypothesis is in many cases additionally supported by the form of the magnitude–frequency distributions for individual faults, constructed from the data of modern earthquake catalogs. At the same time, an important factor affecting the form of the magnitude–frequency distribution is the choice of the spatial domain in which the distribution is constructed. This paper investigates the influence of this factor and determines the conditions under which the Gutenberg–Richter law is applicable for estimating the recurrence of strong earthquakes.

Abstract—A new probabilistic approach to the problem of estimating the regional maximum possible magnitude and some parameters of seismic impact is proposed. The methodology of its practical application is described, which is based on considering the maximum magnitude in the future time interval T as a random quantity and using its quantile with a given level of confidence as the regional maximum magnitude.

This paper examines the response in geomagnetic-field variations caused by the 2020–2023 earthquakes with magnitudes Mw ≥ 7.0 in the Aegean Sea and eastern Turkey. A detailed comparison of high-precision observations of the geomagnetic field and seismograms recorded at complex geophysical observatories within a radius of 3000 km from the epicenters was carried out. The joint analysis involves averaged 1-s data on the rate of change of the magnetic field and records from broadband seismic stations. Their characteristics are assessed in both in time and frequency domains. The spectral characteristics of body and surface waves are separately compared with those of the geomagnetic signal. It is shown that the beginning of disturbance in the magnetic field at each observatory strictly coincides with the arrival of the P-wave and intensifies with the arrival of S-waves. The maximum geomagnetic disturbance is caused by surface waves. The amplitude of electromagnetic excitations is proportional to the amplitude of the parent seismic phases. Thus, the coseismic nature of the observed electromagnetic signal has been confirmed, suggesting its excitation in the Earth’s crust as seismic waves propagate.

The article presents analysis of macroseismic data on the September 21, 2020 (M_w = 5.6) Bystraya earthquake, which occurred in the eastern part of the Tunka basins system on the southwestern flank of the Baikal rift zone. Macroseismic data were collected mainly through an Internet questionnaire posted on the website of the Baikal Branch of the Geophysical Survey, Russian Academy Sciences. A total of 3013 eyewitness responses were collected, which is currently an unprecedented number in the entire history of macroseismic observations in the Baikal region. In total, we collected data for 263 Intensity Data Points. The maximal shaking intensity (VI–VII MSK-64) was observed in the Bystraya village and the Kultuk settlement. The shaking intensity V MSK-64 was noted at a distance of up to ~180 km; intensity IV MSK-64 was recorded at a distance of up to ~550 km. Analysis of data on the Bystraya earthquake revealed significantly lower attenuation compared to that expected from the regional macroseismic equation. Due to the large volume of macroseismic data collected, as well as the high efficiency of the data collection method used, the Bystraya earthquake can be considered an important milestone in macroseismic research in East Siberia.

This paper verifies the compliance of the earthquake productivity law (Shebalin et al., 2020a) in laboratory experiments on rock destruction. Westerly granite and Benheim sandstone specimens were subjected to uniaxial loading under uniform compression. An acoustic-emission (AE) recording system made it possible to create catalogues of AE sources similar to earthquake catalogues. The data from experiments conducted at the Rock Friction Laboratory (USGS, Menlo Park, United States) and the Geomechanics and Rheology Laboratory (GFZ, Potsdam) were analyzed. It was found that the AE events in the considered samples are characterized by a unimodal distribution of the nearest-neighbor proximity function. The compliance of the productivity law for acoustic-emission events in laboratory experiments on the destruction of rock samples is shown, which gives grounds to speak about the similarity of grouping processes in real seismicity and in laboratory conditions.